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Steerable Miniature Legged Robot Driven by a Single Piezoelectric Bending Unimorph Actuator


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In small mobile robots, decreasing the number of
actuators is usually desirable to reduce the size and weight of
the robot, but it is usually at the expense of the robot’s degree
of freedom (DOF). This work presents the development and
preliminary experimental testing of a novel Legged Piezoelectric
Miniature Robot (LPMR) driven only by a single piezoelectric
unimorph actuator and yet fully capable of being maneuvered
to move forward, turn right, or turn left. The underactuated
motion is achieved by exploiting the bending vibration modes
disparity of the piezoelectric actuator at different driving
frequencies and designing specific positions of the robot’s legs
to generate a differential-drive-like mechanism. The speed of
the robot can be controlled through regulating the magnitude
of the applied voltage. The proposed underactuated system is
experimentally verified and a preliminary characterization of
the LPMR in terms of its forward and turning speed versus
applied voltage and payload is investigated and reported

Published in: Engineering
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Steerable Miniature Legged Robot Driven by a Single Piezoelectric Bending Unimorph Actuator

  1. 1. 1 Steerable Miniature Legged Robot Driven by a Single Piezoelectric Bending Unimorph Actuator Audelia G. Dharmawan, Hassan H. Hariri, Shaohui Foong, Gim Song Soh, and Kristin L. Wood IEEE International Conference on Robotics and Automation Singapore May 29 - June 3, 2017
  2. 2. 2 Motivation -10 0 10 20 30 40 50 60 30 50 70 90 110 130 150 TopSpeed(bodylength/s) Body Length (mm) PZT LIPCA Motor *Bubble Size: Robot Mass Our robot 6 actuators Qu et al. 6 actuators Baisch et al. 12 actuators Rios et al. Can we develop a maneuverable piezoelectric miniature robot using only a single actuator? Bidirectional motion using 1 PZT actuator Hariri et al., ICRA 2016 • Mobile robot miniaturization 1 actuator = 1 DOF Over-actuated Basic Robot Architecture PZT Unimorph ActuatorLegs Plot of some existing miniature legged robots
  3. 3. 3 Locomotion Principle • Exploit bending modes of the piezoelectric actuator and leg placement along the robot’s moving direction to achieve bidirectional motion • Further exploit the leg placement on the opposite sides of the mid-sagittal plane to create a differential-drive-like system for steering motion Leg Trajectory Antinode Top view Mid-sagittal plane Mid-sagittal plane Left Turn Right Turn Side view ActuatorLegs Motion Direction Left side of antinode Right side of antinode
  4. 4. 4 Robot Design 𝜑 𝑛 𝑥 = sin(𝛽 𝑛 𝑥) + sinh(𝛽 𝑛 𝑥) − sin 𝛽 𝑛 𝑙 − sinh 𝛽 𝑛 𝑙 cos 𝛽 𝑛 𝑙 − cosh 𝛽 𝑛 𝑙 (cos 𝛽 𝑛 𝑥 + cosh(𝛽 𝑛 𝑥)) ∅ 𝑛 𝑥 = 𝜑 𝑛(𝑥) (𝜌𝐴) 𝑒𝑞 0 𝑙 𝜑 𝑛(𝑥)2 𝑑𝑥 • Mode Shapes𝑓1 𝑓2 𝑓3 Modeshape Length of beam (cm)
  5. 5. 5 Experiment 𝑓𝑛 = 𝛽 𝑛 𝑙 2𝜋𝐿2 (𝐸𝐼) 𝑒𝑞 𝑏(𝜌 𝑝 𝑡 𝑝 + 𝜌 𝑚 𝑡 𝑚) • Resonance Frequencies
  6. 6. 6 Steering Trial